Air-supported vacuum cleaners are known. For example, U.S. Pat. No. 2,751,038 to L. K. Acheson, which issued Jun. 19, 1956 discloses an air-supported vacuum cleaner which has an air space on the underside of the cleaner, which is bounded by the underside of the casing for the cleaner and a peripheral dam or bead. Other air-supported vacuum cleaners are shown in U.S. Pat. No. 2,780,826 to Coons et al., which issued Feb. 12, 1957, U.S. Pat. No. 3,283,355 to I. Jepson, which issued Nov. 8, 1966 and U.S. Pat. No. 2,889,570 to J. E. Duff, which issued Jun. 9, 1959. U.S. Pat. No. 2,743,787 to W. G. Seck, which issued May 1, 1956 discloses an air-supported vacuum cleaner which has an air space bounded by the underside of the casing for the cleaner and a peripheral dam. Outside the peripheral dam there is a deflector for preventing air from discharging across the surface of the floor upon which the vacuum cleaner rests or travels, and for directing the escaping air in an upward direction.
One of the problems with previous air-supported vacuum cleaners is a tendency for the vacuum cleaner to rock or judder as a result of uneven flow of air escaping from under the peripheral dam. One solution to this problem is disclosed in U.S. Pat. No. 2,814,064 to J. C. Montgomery, which issued Nov. 26, 1957 which discloses an air-supported vacuum cleaner with a peripheral double dam with an air diffusing channel between the dams. The air escapes from the air space, past the inner of the two dams and thence through the air diffusing channel. Such an arrangement adds to the cost of the vacuum cleaner and introduces complexity to the operation of the vacuum cleaner. The present invention is directed to a simple but effective air-supported vacuum cleaner which tends to be stable, not subject to juddering and is relatively inexpensive to produce. The invention is also directed to a hover vacuum cleaner with an arrangement which the hover performance tends not to diminish as the filter becomes filled with dust.